Recommendations for the Ready Mixed Producer
Do not use calcium chloride with color pigments. It tends to cause
discoloration/blotches
Keep all raw materials — cement, sand and aggregates especially
— as consistent as possible throughout the entire project. Any change can affect the
final color of the project.
Be sure concrete loads have consistent mix times, and that delivery
and discharge times are a quick as possible. Overmixing, longer that 1-1/2 hours affects
color consistency.
Air content, especially in freeze/thaw climates, should be 5-7%. Air
entrainment is only necessary if your climate dictates
Slump should be consistent and less than 5 inches (125 mm).
Water has a tremendous effect on the final color. Too much water
tends to lighten the color of the project — it looks "pale" or "washed
out". If better flowability is required, use a plasticizer or water reducing
admixture instead.
Clean mixer thoroughly at the end of the job. Begin each new color
with a clean drum.
Do not overload the mixer as this reduces mixing efficiency. By the
same token, mixer should be loaded to a minimum of 40% capacity for a good color mix.
Recommendations for the Contractor Using
Colored Ready Mix
Integrally colored concrete is installed the same way uncolored
concrete is. Follow normal procedures regarding base preparation, use of vapor barriers,
placement of forms, reinforcement and joints. But there are some things that should be
observed.
Be sure to use an experienced ready mixed supplier who consistently
follows the recommendations provided above.
Do not sprinkle dry concentrated pigment onto the surface of
"green" concrete.
Give yourself enough time and adequate labor to do the job right.
Stop floating the concrete when surface becomes wet. Then begin
troweling after bleed water evaporates. If you wait too long, burns or dark spots are
likely.
Avoid adding extra water at the job site. Also, don't wet finishing
tools or sprinkle any water onto the surface of the colored concrete.
Final finishes, such as broom, swirl, rough or imprinting, usually
result in a more uniform color appearance then smooth surfaces.
Do not fog or cover final project with plastic sheets. This tends to
create uneven colors.
Curing compounds are recommended but extreme care must be taken in
their selection and application. Also, surface retarders during finishing may be necessary
in dry, windy weather. For both products, consult your local ready mixed concrete or
admixture supplier for information on products recommended for colored concrete.
Efflorescence is a naturally occurring phenomenon. It is that white
powdery substance, and unfortunately it is more visible on colored concrete products.
Sometimes the whole project looks lighter due to an even layer of efflorescence. Other
times, it occurs in spots or in areas around the edges where faster setting occurred. If
efflorescence happens, care should be taken for its removal. Use a reputable product and
follow recommendations carefully, using all safety precautions.
